Efficient channel estimate based timing recovery

ABSTRACT

A module and method for channel estimate based timing recovery comprises a timing estimation module, a channel estimation module communicably coupled to the timing estimation module, a conversion module communicably coupled to the timing estimation module and to the channel estimation module, and an analog pulse shaping filter communicably coupled to the conversion module, wherein: the analog pulse shaping filter receives an analog signal and outputs a filtered analog signal, the conversion module receives the filtered analog signal and outputs a 1/T rate signal to the channel estimation module, the channel estimation module outputs a 1/T Channel Impulse Response (CIR) estimate to the timing estimation module, and the timing estimation module outputs a timing estimate to the conversion module, wherein the timing estimate is used in conjunction with an output of the conversion module to provide the 1/T rate signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is related to U.S. Provisional PatentApplication 60/628,248 filed on Nov. 16, 2004, entitled Chip-LevelNo-Decision Feedback Equalizer For CDMA Wireless Systems, U.S. patentapplication Ser. No. 11/280,858 filed on Nov. 16, 2005, entitledChip-Level No-Decision Feedback Equalizer For CDMA Wireless Systems, andU.S. patent application Ser. No. 10/796,596 filed on Mar. 9, 2004,entitled Methods and Apparatus For Single Burst Equalization of SingleCarrier Signals In Broadband Wireless Access Systems, the contents ofeach of which are incorporated by reference herein.

BACKGROUND OF INVENTION

In current telecommunication systems, digital information of interest istypically communicated from a transmitter at one location to a receiverat another location by first forming a sequence of symbols based on thedigital information and then using the symbol sequence to modulate asingle carrier signal or a multiple carrier signal. At the receiver, thecarrier signal is removed and the resultant, so called, ‘baseband’signal is processed to recover first the symbols and then the digitalinformation of interest. In general, signals used to communicate digitalinformation from a transmitter to a receiver can be referred to asdigital communication signals. Although the details of the mapping ofthe digital information onto the symbols vary from one application toanother as do the details of the signal modulation, it is standardpractice in the design of digital communication signals to use a fixedsymbol rate (or a well defined set of fixed symbol rates) such that theindividual symbols are used to modulate the signal for a fixed intervalof time. The inverse of this individual symbol time interval is referredto as the symbol rate.

It is also standard practice in the design of digital communicationsignals to place what is referred to as a pulse shaping filter in thetransmitter-to-receiver channel response or equivalently, thetransmitter-to-receiver transfer function. The pulse shaping filterimposes a shape to the individual symbol ‘pulses’ so as to minimize theinterference between the symbol pulses at the communications signalreceiver. By far the most common example of a pulse shaping filter isthe raised cosine filter (RCF). Typically the RCF is distributed betweenthe transmitter and the receiver such that a root raised cosine filter(RRCF) is at both the transmitter and the receiver, the net contributionto the transmitter-to-receiver channel response being equivalent to oneRCF.

It is also standard practice in the design of digital communicationsignals to impose a framing structure on the sequence of symbols that isused to modulate the single carrier or multiple carrier signal. Once theframing structure is properly identified it is an aid to thecommunications signal receiver in that it simplifies the process ofextracting the digital information of interest. An example of such aframing structure is the ‘slot’ structure in the Wideband Code DivisionMultiple Access (WCDMA) signal specified by the Third GenerationPartnership Project (3GPP) standards organization. The WCDMA slotconsists of 10 sub-frames of 256 chips each, the symbols being relatedto the chips by a spread code. For the WCDMA signal and code divisionmultiple access signals in general, the fundamental timing interval isthe chip rate whereas the symbol rates are well defined multiples of thechip rate.

Symbol (chip) timing recovery refers to the process in thecommunications signal receiver that estimates the time when theinformation and/or energy associated with individual symbols (chips)arrives in the received communications signal. Since the transmittertypically clocks the symbol (chip) interval based on a crystaloscillator, in order to be accurate the timing recovery process at thereceiver must be capable of dynamically tracking changes in thefundamental timing interval that are due to variations in thetransmitter's crystal oscillator frequency.

Frame timing recovery refers to the process in the communications signalreceiver that estimates when the start and stop of each frame orsub-frame occurs in the received communications signal.

If the communications signal receiver is battery operated it isdesirable to process the communications signal at a low sample rate inorder to reduce the computations per symbol (digital information ofinterest). Fewer computations per symbol result in lower powerconsumption by the receiver and extend the battery life. This isespecially desirable for today's mobile broadband communication devices,examples being third generation (3G) mobile phones and battery operatedcomputers with embedded wireless broadband network interfaces.

Symbol timing recovery for the above described digital communicationssignals is an important function. However, traditional timing recoveryschemes require an over-sampling of the communications signal, e.g., asampling at a rate of 2/T or 4/T, resulting in various inefficiencies.As such, what is needed is a system and method that overcomes thislimitation.

SUMMARY OF INVENTION

The present invention provides a system (or module) and method of anefficient channel estimate based timing recovery for digitalcommunications signals when the signal is sampled at a minimum rate ofone sample per fundamental timing interval (i.e., at a 1/T sample rate).The present invention also provides an efficient frame timing recoveryfor digital communication signals.

In one embodiment of the present invention, a module comprises a timingestimation module, a channel estimation module communicably coupled tothe timing estimation module, a conversion module communicably coupledto the timing estimation module and to the channel estimation module,and an analog pulse shaping filter communicably coupled to theconversion module, wherein: the analog pulse shaping filter receives ananalog signal and outputs a filtered analog signal, the conversionmodule receives the filtered analog signal and outputs a 1/T rate signalto the channel estimation module, the channel estimation module outputsa 1/T Channel Impulse Response (CIR) estimate to the timing estimationmodule, and the timing estimation module outputs a timing estimate tothe conversion module, wherein the timing estimate is used inconjunction with an output of the conversion module to provide the 1/Trate signal.

In another embodiment of the present invention, a module comprises aninterpolation filter, a timing estimation module communicably coupled tothe interpolation filter, and a channel estimation module communicablycoupled to the interpolation filter, and to the timing estimationmodule, wherein: the interpolation filter receives a digital signal andoutputs a 1/T rate signal to the channel estimation module, the channelestimation module outputs a 1/T Channel Impulse Response (CIR) estimateto the timing estimation module, and the timing estimation moduleoutputs a timing estimate to the interpolation filter, wherein thetiming estimate is used in conjunction with the digital signal toprovide the 1/T rate signal.

In a further embodiment of the present invention, a module comprises aninterpolation filter, a module communicably coupled to the interpolationfilter, a timing estimation module communicably coupled to theinterpolation filter, and a channel estimation module communicablycoupled to the module, to the interpolation filter, and to the timingestimation module, wherein: the interpolation filter receives a digitalsignal and outputs a one sample per baud interval (1/T) rate signal tothe module and to the channel estimation module, the channel estimationmodule outputs a Channel Impulse Response (CIR) estimate to the timingestimation module, and the timing estimation module outputs a timingestimate to the interpolation filter.

In yet another embodiment of the present invention, a method fordetermining a timing estimate comprises receiving a 1/T sampled channelwaveform estimate, interpolating the 1/T sampled channel waveformestimate to an N/T sampled channel waveform estimate, determining anabsolute value waveform based on the interpolating, and determining atiming estimate based on the absolute value waveform.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a first block diagram of a channel estimate based timingrecovery system in accordance to an embodiment of the present invention;

FIG. 2 depicts a second block diagram of a channel estimate based timingrecovery system in accordance to an embodiment of the present invention;

FIG. 3 depicts a third block diagram of a channel estimate based timingrecovery system in accordance to an embodiment of the present invention;

FIG. 4 depicts a fourth block diagram of a channel estimate based timingrecovery system in accordance to an embodiment of the present invention;

FIG. 5 depicts a flow chart for outputting a 1/T resolution channelestimate in accordance to an embodiment of the present invention;

FIG. 6 depicts a first flow chart for obtaining a timing estimate from a1/T resolution channel estimate in accordance to an embodiment of thepresent invention;

FIG. 7 depicts a second flow chart for obtaining a timing estimate froma 1/T resolution channel estimate in accordance to an embodiment of thepresent invention;

FIG. 8 depicts a third flow chart for obtaining a timing estimate from a1/T resolution channel estimate in accordance to an embodiment of thepresent invention; and

FIG. 9 depicts a fourth flow chart for obtaining a timing estimate froma 1/T resolution channel estimate in accordance to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system (or module) and method of anefficient channel estimate based timing recovery for digitalcommunications signals when the signal is sampled at a minimum rate ofone sample per fundamental timing interval (i.e., at a 1/T sample rate).The present invention can be utilized with any wireless signal thatutilizes a fixed timing interval which includes Code Division MultipleAccess (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA),and Orthogonal Frequency Division Multiplexing (OFDM).

For a transmitter-to-receiver channel that includes a pulse shapingfilter for a pulse interval T equal to the fundamental timing interval,timing recovery is accomplished with a signal that is sampled at theminimum rate of one sample per fundamental timing interval (i.e., a 1/Tsample rate). The timing estimate is obtained by producing a minimalresolution channel estimate waveform from the 1/T sample rate signalwherein the resolution of the channel estimate waveform is one time-lagsample per fundamental timing interval and applying a timing estimationprocedure to the minimal resolution channel estimate waveform.

FIG. 1 shows a block diagram of certain processes performed by animplementation of the minimum sample rate, channel estimate based timingrecovery system 100 of the present invention. In the processconfiguration of FIG. 1, an analog pulse shaping filter 110 receives theanalog input signal and outputs a filtered analog signal that isreceived by the minimum 1/T rate analog-to-digital conversion module120.

For example, the analog input signal in FIG. 1 can represent a basebandsignal associated with the WCDMA downlink in which case it represents,equivalently, either one complex signal or two real signals representingthe in-phase and quadrature components of the analog baseband signalthat is output from a radio frequency (RF) analog signal down convertersuch as exists in a cell phone handset. In this example the 1/T samplerate is equal to the WCDMA chip rate and the analog pulse shaping filter110 is a RRCF. Since the WCDMA transmitter has a matching RRCF pulseshaping filter, the transmitter-to-receiver channel includes a net RCFpulse shaping filter equal to the product of two RRCF pulse shapingfilters.

The pulse shaping filter can be described as belonging to the set offilters that tend to minimize the interference between the symbol pulsesin the output of the filter. For example, for baseband signals the pulseshaping filter is a low pass filter with a cutoff frequency ofapproximately ½T.

Referring to FIG. 1, the minimum 1/T rate analog-to-digital conversionmodule 120 also receives the timing estimate from the timing estimationmodule 140. The timing estimate is used to adjust the timing phase ofthe analog-to-digital conversion process. For example, if the signalinput to the analog-to-digital conversion module 120 is y(t) where t iscontinuous time, the 1/T rate sampled output of the module 120 can berepresented as y(n*T+α) where α is the timing phase such that 0<=<=T. Inthe case where T is perfectly known, the timing estimate can adjust thetiming by simply adjusting α. In the more general case where T is notperfectly known, a sequence of timing estimates in effect adjusts both Tand α in order to provide an optimally sampled 1/T rate signal.

The timing estimation module receives the minimum 1/T resolution channelimpulse response (CIR) estimate waveform from the channel estimationmodule 130. For the example, this CIR estimate waveform can be notatedas a set of complex (or real) numbers, ĥ(τ), at discrete time lags τ=n*Tfor n=0, 1, 2, . . . N_(CIR), where T is the fundamental timing intervaland the discrete time lags are such that the actual channel impulseresponse, h(τ), is known to be zero for n outside of the interval n=0 toN_(CIR). The channel estimation module 130 receives the 1/T sample ratesignal from the 1/T rate analog-to-digital conversion module 120 andprocesses it as described below to determine the 1/T resolution CIRestimate, ĥ(τ).

The minimum sample rate, channel estimate based timing recovery system100 of FIG. 1 outputs a timing optimized 1/T rate signal from theanalog-to-digital conversion module 120 that can be processed further asis appropriate for specific applications. For example, if the analogsignal input is the baseband WCDMA downlink signal, the optimized 1/Trate output signal can be efficiently processed to provide symbolestimates to a decoder unit in a cellphone handset. The decoder andsubsequent processing units in the cellphone or other electronic devicecan then process the information in the symbol estimates to provide thesubscriber, for example, a visual display showing a text message, e-mailor video clip; and/or audible sounds representing a voice phone call,video soundtrack or music clip.

FIG. 2 illustrates a minimum sample rate, channel estimate based timingrecovery system 200 that is implemented for multiple signals usingsimilar processing modules as in FIG. 1. The filtered analog signal thatis output from the analog pulse shaping filter 210 is received bymultiple signal timing recovery subsystems numbered as 1 to N, with onlythe 1^(st) and N^(th) timing recovery subsystems, 201 and 202 beingshown explicitly in FIG. 2.

An example application for the type of multiple signal implementationshown in FIG. 2 is a single antenna interference canceller basebandreceiver in which multiple interfering radio signals are jointly presentin and processed from an input analog signal obtained from a singleantenna. The ability of the present invention to provide timing recoveryfor multiple signals and/or dispersive channels (e.g., wireless channelsthat distort the received signal) is of significant importance sinceeach of these requirements are known to be difficult to fulfill.

FIG. 3 illustrates an alternative implementation of the minimum samplerate, channel estimate based timing recovery system 300 for multiplesignals. In the implementation of FIG. 3, the input analog signal isreceived by a higher rate analog-to-digital conversion module 305 thatoutputs a higher rate digital signal that is received by a digital pulseshaping filter 310. The term ‘higher rate’ refers to sample rates equalto or greater than 2/T, i.e., at least two samples per fundamentaltiming interval T.

The digital pulse shaping filter 310 provides the higher rate digitalsignal that is received by multiple signal timing recovery subsystemsnumbered as 1 to N, with only the 1^(st) and N^(th) signal timingrecovery subsystems, 301 and 302, being shown explicitly. Theinterpolation filters 320 and 350 receive in common the higher ratedigital signal that is output from the digital pulse shaping filter 310and receive separately the local timing estimates that are output fromthe timing estimation modules 240 and 370, respectively. The timingestimation modules 240 and 370 receive the 1/T resolution CIR estimatesfrom the channel estimation modules 330 and 360 which in turn receivethe 1/T rate signal from the interpolation filters 320 and 350,respectively.

Comparing the implementations of FIGS. 2 and 3, the implementation ofFIG. 2 has N functionally separate 1/T rate analog-to-digital conversionmodules, one analog filter and no digital filters whereas theimplementation of FIG. 3 has one M/T rate analog-to-digital conversionmodule (M≧2) and 2*N+1 digital filters where N is the number of multiplesignals being processed from the single analog input signal.

FIG. 4 illustrates another alternative implementation of the minimumsample rate, channel estimate based timing recovery system 400, which ispresented for a single signal timing recovery application. Comparing theimplementation of FIG. 4 to that of FIG. 3, an analog pulse shapingfilter 410 receives the analog input signal and provides a filteredanalog signal to the higher rate (M/T rate, M≧2) analog-to-digitalconversion module 420, eliminating the need for the digital pulseshaping filter 310. The implementation in FIG. 4 can be extended tomultiple (N) signal timing recovery applications by replicating thetiming recovery subsystem 401 so as to provide N such subsystems as wasdone previously in FIGS. 2 and 3. Other implementations of the minimumsample rate, channel estimate based timing recovery system can beconsidered by one trained in the art.

FIG. 4 also illustrates that the motivation for generating a timingoptimized 1/T rate signal is to output this signal to a signalprocessing module 410 that is application specific. For example,returning to the WCDMA user device application, the signal processingmodule can represent a process that inputs the timing optimized 1/T ratesignal and outputs raw symbol estimates to the decoder units that aredescribed in the appropriate 3GPP specification for WCDMA. In thisexample and others, the signal processing module can take advantage ofthe availability of the 1/T resolution CIR estimate generated by thechannel estimation module 450.

Furthermore, if the channel estimation module 450 uses a signal framebased reference signal 440 to estimate the channel as discussed below,then the timing estimation module 460 can provide a framesynchronization signal that can be used to advantage by the signalprocessing module 410. Considering the WCDMA downlink receiverapplication example, it is known that the CPICH pilot is intended forchannel estimation. In this example, the known base station scramblecode can be used as the frame reference signal 440 allowing the timingestimation module 460 to provide a frame synchronization signal markingthe 256 chip sub-frame of the WCDMA signal.

FIG. 5 illustrates certain functions performed by the channel estimationmodule 500. In block 510 the 1/T rate sampled signal that represents thechannel output is received from, for example, either a 1/T rateanalog-to-digital conversion module or a 1/T rate digital interpolationfilter. A known reference signal is also accessed in block 520 thatrepresents the channel input. The known reference signal and the 1/Trate sampled signal can be processed by a number of data aided channelestimation procedures or other known channel estimation procedures whichmay be applied in block 530. The output of the channel estimationalgorithm is a raw channel estimate waveform that is a set of complex(or real) numbers that can be notated as, ĥ_raw(τ), at discrete timelags τ=n*T for n=0, 1, 2 . . . N_(CIR).

Referring to FIG. 5, the averaging block 540 receives a sequence of theraw channel estimate waveforms from the channel estimation algorithm 530and performs an averaging to improve the quality of the channelestimate. Block 550 outputs the averaged channel estimate as a 1/Tresolution waveform that can be notated as a set of complex (or real)numbers, ĥ(τ), at discrete time lags τ=n*T for n=0, 1, 2 . . . N_(CIR).

Note that the presence of the pulse shaping filter in the channel hasthe consequence that the 1/T resolution channel estimate waveform, ĥ(τ)at discrete τ=n*T for n=0, 1, 2 . . . N_(CIR), is effectively a samplingof the channel impulse response and contains the timing phaseinformation for the reference signal used in the channel estimationmodule. For example, in the WCDMA baseband receiver application, thetransmitter-to-receiver channel h(τ) is the convolution of the RFpropagation channel and a low pass filter of cutoff frequency 1/(2*T).In this example the 1/T resolution channel estimate can be obtainedusing the CPICH pilot as a reference signal. The resulting 1/Tresolution channel estimate contains the timing phase information thatallows a precision estimate of the timing of the CPICH pilot in the 1/Tsample rate signal of interest (e.g., the 1/T sample rate signal inFIGS. 1 to 4).

It is novel to think of a 1/T sample rate signal as containing timingphase information for a digital communications signal with fundamentaltiming interval T. It is generally thought that a sample rate of atleast a 2/T is required to recover the timing phase of the fundamentaltiming interval T. Once it is realized that the detailed timinginformation for the reference signal used to compute the channelestimate is contained in the 1/T resolution channel estimate, methodscan be defined for estimating the timing. FIGS. 6, 7, 8 and 9 illustratemethods for obtaining the timing estimate from a 1/T resolution channelestimate.

FIG. 6 illustrates processes in the timing estimation module 600. The1/T resolution channel estimate waveform, ĥ(τ), is received 610 and anabsolute value channel estimate waveform, |ĥ(τ)|, is determined 630,such that |ĥ(τ)|={real(ĥ(τ))²+imag(ĥ(τ))²}^(1/2) where real( ) and imag() provide the real and the imaginary parts of the possibly complexvalued ĥ(τ). Approximate methods can be used for determining themagnitude waveform, |ĥ(τ)|. An example is: |ĥ(τ)|≅A*max(I,Q)+B*min(I,Q)where I=real(ĥ(τ)), Q=imag(ĥ(τ)), where A=0.9605 and B=0.3979. Block 640in FIG. 6 determines the timing estimate from the absolute value channelestimate waveform, |ĥ(τ)|, using methods described below and illustratedin FIGS. 7, 8 and 9.

Referring to FIG. 7, the plot 701 is a representation of both theestimated |ĥ(τ=n*T)| and the actual |h(τ)| versus r. The estimate|ĥ(τ=n*T)| is available at discrete time lags τ=n*T for n=0, 1, 2 . . .N_(CIR). For example, 710 represents the value of |ĥ(τ=n*T)| at n=3. Theactual, but unknown |h(τ)| is shown as a continuous curve 720 forcontinuous τ. Due to the presence of the pulse shaping filter, curve 720is known to be a well behaved, slowly changing smooth curve for all τbetween the τ=n*T measurement points.

Referring to FIG. 8, a suitable method of determining the timingestimate 800 involves first finding the maximum of |ĥ(τ=n*T)| 830 andthen determining a sum from |ĥ(τ=n*T)| data on the left hand (LHS) sideof the maximum and a sum from |ĥ(τ=n*T)| data on the right hand side(RHS) of the maximum 840. As illustrated in 701 of FIG. 7, the maximumof |ĥ(τ=n*T)| occurs at n_(max)=4 notated as 730 and we define a 3*Tlength range 740 for determining Σ_(LHS)=the LHS sum of |ĥ(τ=n*T)| dataand a 3*T length range 750 for determining Σ_(RHS)=the RHS sum of|ĥ(τ=n*T)| data. An offset is then determined 840 from a formula thatinputs Σ_(LHS) and Σ_(RHS). An example of a suitable formula is:offset=A*(Σ_(RHS)−Σ_(LHS))*Toffset=max([−T,min([+T,offset])])where A is a positive constant; max( ) and min( ) pick the maximum andminimum, respectively. The latter expression bounds the offset to +/−T.As illustrated in 702 of FIG. 7, this restricts the timing estimate 760to be within +/−T of the location of maximum. This restriction tends tomaximize the energy available for subsequent processing of the timingoptimized 1/T rate signal. The timing estimate is then determined inblock 850 as timing estimate=n_(max)*T+offset. Other ranges for the LHSand RHS sums can be used and other more complicated formulas for theoffset can be used within the same design 800 for determining the timingestimate shown in FIG. 8. The LHS and RHS ranges and the parameters inthe formulas can be found experimentally using least squared errortechniques to improve the statistical agreement of the timing estimatedata from the formulas with timing estimate data obtained fromalternative known timing recovery procedures.

FIG. 9 illustrates processes an alternative implementation of the timingestimation module 900. The 1/T resolution channel estimate waveform,ĥ(τ), is received 910 and an interpolation is performed 920 in order tocreate a higher resolution channel estimate waveform that is defined atN time lags in each time lag interval T where N≧2. This N/T resolution,interpolated channel estimate waveform, ĥ_i(τ=m*T/N) for m=0, 1, 2 . . .N*N_(CIR,) has the property that when m=0, N, 2*N, . . . N_(CIR.)*N itis equal to the original 1/T channel estimate waveform ĥ(τ=n*T) n=0, 1,2 . . . N_(CIR) that is a 1/T resolution estimate of the actual channelimpulse response, h(τ) at each τ=n*T. Given the presence of the pulseshaping filter in the channel and provided a conservative interpolationtechnique is applied, at other values of m, the higher resolutionĥ_i(τ=m*T/N) is also a reasonable approximation to the actual channelimpulse response, h(τ) at each τ=m*T/N. This provides that any knownmethod for determining the timing estimate from a higher (i.e., N/T withN≧2) resolution channel estimate can be applied to the ĥ_i(τ=m*T/N)waveform. For example the absolute value channel estimate waveform|ĥ_i(τ=m*T/N)|, for m=0, 1, 2 . . . N*N_(CIR,) can be determined 920 andthe method of finding the value of m=m_(Y) that maximizes asignal-to-interference-plus-noise ratio (SINR) formula defined as:Y=|ĥ _(—) i(m*T/N)|²/(Σ|ĥ _(—) i(n*T/N)|²+2*N _(O))where the summation (Σ) is n=m−K*N, m−(K−1)*N, . . . m−N. Note that thetiming estimation method utilizing this formula requires over-samplingat a rate of N samples per fundamental timing interval T to produce ahigher (i.e., N/T with N≧2) resolution channel estimate whereas themethods and systems of the present invention provide a timing estimategiven the minimal 1/T sample rate. According to the present inventionthe above formula and other ad-hoc formulas can be used to determinetiming estimates from the interpolated channel impulse response estimatethat is derived from a minimally sampled 1/T rate digital signal asexplained herein.

Although embodiments of the present invention have been illustrated inthe accompanied drawings and described in the foregoing detaileddescription, it will be understood that the invention is not limited tothe embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions without departing from the spirit ofthe invention as set forth and defined by the following claims. Forexample, the channel estimation can be performed via hardware and/orsoftware using a processor such as a Reduced Instruction Set Computer(RISC) or a Digital Signal Processor (DSP). Further, although depictedin a particular manner, more than one of the modules can be utilized inthe present invention and functionality provided by one module can befully and/or partially provided by another one of the modules. Also, thetransfer of information from one module to another module can beperformed by a wired or a wireless connection.

1. A module, comprising: a timing estimation module; a channelestimation module communicably coupled to the timing estimation module;a conversion module communicably coupled to the timing estimation moduleand to the channel estimation module; and an analog pulse shaping filtercommunicably coupled to the conversion module; wherein: the analog pulseshaping filter receives an analog signal and outputs a filtered analogsignal; the conversion module receives the filtered analog signal andoutputs a 1/T rate signal to the channel estimation module; the channelestimation module outputs a 1/T Channel Impulse Response (CIR) estimateto the timing estimation module; and the timing estimation moduleoutputs a timing estimate to the conversion module, wherein the timingestimate is used in conjunction with an output of the conversion moduleto provide the 1/T rate signal.
 2. The module of claim 1, wherein theoutput of the conversion module is a digital signal.
 3. The module ofclaim 1, wherein the conversion module is a higher rateanalog-to-digital conversion module.
 4. The module of claim 1, whereinthe 1/T rate signal is at least one of: a timing optimized outputsignal; and a minimum rate signal.
 5. The module of claim 1, wherein the1/T rate signal is sent to a user associated with the module.
 6. Amodule, comprising: an interpolation filter; a timing estimation modulecommunicably coupled to the interpolation filter; and a channelestimation module communicably coupled to the interpolation filter, andto the timing estimation module; wherein: the interpolation filterreceives a digital signal and outputs a 1/T rate signal to the channelestimation module; the channel estimation module outputs a 1/T ChannelImpulse Response (CIR) estimate to the timing estimation module; and thetiming estimation module outputs a timing estimate to the interpolationfilter, wherein the timing estimate is used in conjunction with thedigital signal to provide the 1/T rate signal.
 7. The module of claim 6comprising a conversion module communicably coupled to the interpolationfilter.
 8. The module of claim 7 wherein the conversion module is ahigher rate analog-to-digital module.
 9. The module of claim 7 whereinthe conversion module receives an analog signal.
 10. The module of claim6, wherein the 1/T rate signal is at least one of: a timing optimizedoutput signal; and a minimum rate signal.
 11. A module, comprising: aninterpolation filter; a module communicably coupled to the interpolationfilter; a timing estimation module communicably coupled to theinterpolation filter; and a channel estimation module communicablycoupled to the module, to the interpolation filter, and to the timingestimation module; wherein: the interpolation filter receives a digitalsignal and outputs a one sample per baud interval (1/T) rate signal tothe module and to the channel estimation module; the channel estimationmodule outputs a Channel Impulse Response (CIR) estimate to the timingestimation module; and the timing estimation module outputs a timingestimate to the interpolation filter.
 12. The module of claim 11,wherein the module is at least one of: a signal processing module; ademodulator module.
 13. The module of claim 12 wherein the demodulatormodule outputs data.
 14. The module of claim 13 wherein the output datais received by a user.
 15. The module of claim 14 wherein the user isassociated with the module.
 16. A method for determining a timingestimate, comprising: receiving, via a receiver, a 1/T sampled channelwaveform estimate; interpolating, via an interpolating filter, the 1/Tsampled channel waveform estimate to an N/T sampled channel waveformestimate; determining an absolute value waveform based on theinterpolating; and determining a timing estimate, via a timingestimation module, based on the absolute value waveform.
 17. The methodof claim 16 comprising outputting the timing estimate to at least oneof: a conversion module; the timing estimation module; another timingestimation module; a timing error detector; and a timing recoverymodule.
 18. The method of claim 16, wherein N is greater than
 1. 19. Themethod of claim 16, wherein N is around 8 to around
 64. 20. The methodof claim 16, wherein the 1/T sampled channel waveform estimate is basedupon an analog pulse shaped filtered signal.